CPC C07D 231/44 (2013.01) | 18 Claims |
1. A process for the synthesis of fipronil, the process comprising the following steps:
a) reacting trifluoromethane sulfinyl chloride with 5-amino-3-cyano-1-(2,6-dichloro-4-trifluoromethylphenyl)-pyrazole and amine hydrochloride in a halogenated fluid medium to obtain a reaction mixture;
b) cooling said reaction mixture to a temperature in the range of 20° C. to 35° C. to obtain a cooled reaction mixture;
c) adding a mixture of said halogenated fluid medium and water to said cooled reaction mixture to obtain an admixture;
d) neutralizing said admixture with a neutralizing agent to obtain a biphasic mixture containing an organic phase and an aqueous phase;
e) separating said organic phase comprising fipronil followed by cooling said separated organic phase to a temperature in the range of 2° C. to 30° C. to obtain a precipitate of fipronil; and
f) filtering said precipitate to obtain a solid, washing said solid and drying said washed solid to obtain fipronil with purity in the range of 95% to 97%;
wherein the amount of 5-amino-1-(2,6-dichloro-4-trifluoromethylphenyl)-3-cyano-4-trifluoromethylsulfonyl pyrazole in the fipronil is in the range of 0% to 0.5%.
|